Loike J D, Somes M, Silverstein S C
Am J Physiol. 1986 Jul;251(1 Pt 1):C128-35. doi: 10.1152/ajpcell.1986.251.1.C128.
The uptake of creatine in human monocytes and monocyte-derived macrophages can be divided into two components. One component of uptake is saturable (Km = 30 microM), specific for creatine, requires Na+ in the extracellular medium, and enables cells to take up creatine against a concentration gradient of creatine. The second component of uptake is nonsaturable and accounts for less than 10% of creatine uptake at physiological creatine concentrations (20-60 microM). Both monocytes and macrophages have similar Km values for creatine transport. However, macrophages exhibit a fivefold greater rate of creatine uptake than monocytes (3.6 vs. 0.7 pmol X micrograms protein-1 X h-1), indicating that monocyte differentiation into macrophages is associated with an increase in the number of creatine transporters in the membrane. Monocytes do not contain creatine kinase and do not phosphorylate creatine; monocyte-derived macrophages express creatine kinase and phosphorylate approximately 25% of intracellular creatine. These results and the finding that 2-deoxyglucose inhibits creatine phosphorylation by macrophages without affecting the transport of creatine indicate that phosphorylation of creatine is not required for net creatine accumulation.
人体单核细胞和单核细胞衍生的巨噬细胞对肌酸的摄取可分为两个部分。摄取的一个部分是可饱和的（Km = 30微摩尔），对肌酸具有特异性，细胞外培养基中需要Na +，并使细胞能够逆着肌酸浓度梯度摄取肌酸。摄取的第二个部分是不饱和的，在生理肌酸浓度（20 - 60微摩尔）下占肌酸摄取的不到10%。单核细胞和巨噬细胞对肌酸转运的Km值相似。然而，巨噬细胞摄取肌酸的速率比单核细胞高五倍（3.6对0.7皮摩尔×微克蛋白-1×小时-1），这表明单核细胞分化为巨噬细胞与膜中肌酸转运体数量的增加有关。单核细胞不含有肌酸激酶，也不使肌酸磷酸化；单核细胞衍生的巨噬细胞表达肌酸激酶，并使约25%的细胞内肌酸磷酸化。这些结果以及2 - 脱氧葡萄糖抑制巨噬细胞对肌酸的磷酸化而不影响肌酸转运的发现表明，肌酸的净积累不需要肌酸磷酸化。
